Z39.50 Implementor Agreement
Requesting XML Records
This is an implementor argreement pertaining to the retrieval of XML records where the XML schema (or DTD or some other form of definition) is identified by means of the element set name parameter (Small-set-element-set-names or Medium-set-element-set-names in a Search request, or Element-set-names in a Present request). It does not address the use of the Comp-spec parameter for this purpose. If Comp-spec is used, this agreement does not apply.
Agreement: To retrieve XML records, supply the object identifier 1.2.840.10003.5.112 (XML-b), as the record syntax, and supply a globally unambiguous identifier of the desired XML definition as the element set name.
The globally unambiguous identifier may but need not be a URI. If a URI, it may, but need not be the locator of an XML schema definition or DTD. (And if a URI, it need not be an HTTP URI.)
- The identifier "http://www.loc.gov/zing/srw/dcschema/v1.0/" would be used as the element set name to indicate the schema at http://www.loc.gov/z3950/agency/zing/srw/dc.xsd.
- The identifier"http://www.loc.gov/mods/" would be used as the element set name to indicate the schema at: http://www.loc.gov/standards/mods/mods.xsd.
- The identifier: "http://www.editeur.org/onix/ReferenceNames" would be used as the element set name to indicate the dtd at http://www.editeur.org/onix/2.0/reference/onix-international.dtd.
- The identifier: "http://www.kb.nl/persons/theo/dcx/" would be used as the element set name to indicate that records are to be composed according to the definition at that URI (http://www.kb.nl/persons/theo/dcx).
- The identifier "urn:xmldef:12345" might identify some xml defintion. This is a fictitious example which presumes that a URN namespace identifier "xmldef" would be registered (there is no such namespace).
Note, particularly for examples 1-3, it is the identifiers, and not the URIs of the schemas or DTDs, that are to be used as element set names. These identifiers, syntactically, are URIs, however they are not necessarily actionable URIs. Examples 1-3 originate from the table at http://www.loc.gov/z3950/agency/zing/srw/records.html. For example 1, the identifier is not actionable and cannot be followed. For example 2, the URI is actionable but following it does not help to determine its meaning as an element set; likewise for example 3. For example 4, the identifier does happen to be an actionable URI pointing to the desired definition.
The general rule then, is that when the record syntax is 1.2.840.10003.5.112, the XML definition (schema, dtd, etc) is identified either from URIs Identifying XML Definitions used as Z39.50 ESNs maintained by the Z39.50 Maintenance Agency or from some similar page maintained elsewhere.
The Maintenance Agency does not attempt to list all such identifiers used, but does try to maintain those of general use.